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  1. #1
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    home brewed battery back - 18650? 26650?

    I'm looking to piece together a couple battery packs. I've been looking at building a 4cell 26650 trustfire 5000mAh (4000mAh) as i've seen good reviews on them. considering the weight and cost, would I be better just going with a set of 18650s?

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    Kind of a tough question to answer with knowing more about your goals, configuration, budget etc. The best 26650s that I have looked at have lower energy density the best 18650s. Six 18650s create a pack that is smaller (less volume) than four 26650s but can provide about 20% more power. The downside is it costs at least double for the 18650s. Also six 18650s can not be be used in a setup requiring 14.4V.

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    Quote Originally Posted by sixteenornumber View Post
    I'm looking to piece together a couple battery packs. I've been looking at building a 4cell 26650 trustfire 5000mAh (4000mAh) as i've seen good reviews on them. considering the weight and cost, would I be better just going with a set of 18650s?
    I've thought about this myself a time or two and considered the *trade-offs ( *cost/quality/weight ). Finally I decided if I was to go through all the trouble to build my own battery that I would want the lightest/most compact set-up I could come up with and still get good run time. My conclusion was that I would likely build the battery using the best Panasonic 18650 cells.

    If building a 7.4 volt battery with the best Panasonic 18650 cells ( 4 cells ) you would get a real 6200mAh battery. If you need more run time a 6 cell would be the next step and get you about 9300mAh. If I needed more than that I either go with the 4-cell 26650 as you proposed or just carry another 4-cell 18650 battery as back-up.

    If you really are into longer epic type night time riding having a bigger
    battery ( or back-up ) is a good idea. Personally I now have the option to extend my rides by just carrying along an extra 2-cell battery. Not that I really need to do that because most of my night rides are usually not more than three hours long and the 4-cell batteries I use have never let me down.

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    Quote Originally Posted by Cat-man-do View Post
    If building a 7.4 volt battery with the best Panasonic 18650 cells ( 4 cells ) you would get a real 6200mAh battery. If you need more run time a 6 cell would be the next step and get you about 9300mAh. If I needed more than that I either go with the 4-cell 26650 as you proposed.
    The best Panasonic 18650 is now a 3400mA cell. That puts a 7.4V four cell pack at 6800mA capacity and a six cell pack at 10,200mA. Since the best 26650s I have heard about so far are really 4000mA (despite what the label says), you'll have 8000mA. Six 18650s make a smaller/lighter pack with 20% more power than four 26650s. Now if only Panasonic would get into building 26650s......

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    I just got a couple of ebay lights to replace my aging stellas. The lights I bought have a T6 and an R5 in a single housing. the beam pattern is quite nice and far better than the single T6 lights that friends have.

    I really do love this light but the battery is worthless. I used a voltage meter to measure the battery life on each of the settings (picture below). High = T6+R5, Medium = T6 and finally Low = R5.

    I looked up the specs on the R5 and it appears to be about 50% of what the T6 is. from the graph, anyone have any idea what the mAh rating is on my battery pack? Its a 2 series/2 parallel pack.




  6. #6
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    Quote Originally Posted by sixteenornumber View Post
    from the graph, anyone have any idea what the mAh rating is on my battery pack? Its a 2 series/2 parallel pack.
    Without current numbers it's hard to get very close. Assuming the XML is at 3A and the XPG is at 1.5A that's about 14W on the high setting. Since the graph shows 1 hr on high that is 14W/hr. A 7.4V 1900mA battery has 14W/hr capacity. Therefore I would say your pack is 1900 mA. That means either 950mA cells (junk) or it has a bad cell in it (quite likely).

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    Quote Originally Posted by Vancbiker View Post
    Without current numbers it's hard to get very close. Assuming the XML is at 3A and the XPG is at 1.5A that's about 14W on the high setting. Since the graph shows 1 hr on high that is 14W/hr. A 7.4V 1900mA battery has 14W/hr capacity. Therefore I would say your pack is 1900 mA. That means either 950mA cells (junk) or it has a bad cell in it (quite likely).
    2 questions,

    1) I've seen some batteries like the Panasonics go for a little too much money. I would like to get at least 3 hours out of a pack, can you recommend some 18650s?

    2) anyone know where I can buy the female side of the power cable for the pack?

    :::EDIT:::
    you were 100% right on the bad cell thing. i wasn't paying attention to which battery pack (i have 2) I used for the tests. I'm retesting the medium and high on the other battery pack. I'm 30min in right now and so far it's looking like it's going to last 2 times as long. I'll update when i'm done.

  8. #8
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    Quote Originally Posted by sixteenornumber View Post
    2 questions,

    1) I've seen some batteries like the Panasonics go for a little too much money. I would like to get at least 3 hours out of a pack, can you recommend some 18650s?

    Sanyo, Samsung, Sony, and others have pretty good lower cost cells in the 2600mA range. The older 2900mA Panasonics seem to be reasonably priced to me. Finding a legitimate supplier is difficult it seems. Lots of bogus cells out there.

    I have some Chinese ultrafires that are marked 2400mA that are really about 1800mA. I have done the laptop battery salvage thing with good results. That said however, the last set of batteries I bought were protected Panasonic 3400s from Callies Kustoms. Expensive yes, but in my use (not running on high all the time) are lasting twice as long as the Ultrafires. I'm going to build new holder setups with fewer cells for smaller, lighter packs without giving up runtime.

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    im having the same problem with finding a legitimate supplier. i see a lot of $16 cells on ebay that "look" like pansonics but I don't believe it. right now im thinking the best way would be to buy a battery pack straight from HP or Dell and salvage them.

    this seems ok but i really have no idea...
    2X Panasonic 18650 3 6V 3400mAh Rechargeable Li ion Battery NCR18650B 3100 | eBay

  10. #10
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    Quote Originally Posted by sixteenornumber View Post
    im having the same problem with finding a legitimate supplier.

    You could look at budget light forum or candlepower forum for suppliers. That's where I heard about Callies Kustoms.

  11. #11
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    Quote Originally Posted by Vancbiker View Post
    The best Panasonic 18650 is now a 3400mA cell. That puts a 7.4V four cell pack at 6800mA capacity and a six cell pack at 10,200mA. Since the best 26650s I have heard about so far are really 4000mA (despite what the label says), you'll have 8000mA. Six 18650s make a smaller/lighter pack with 20% more power than four 26650s. Now if only Panasonic would get into building 26650s......
    Yes, I know about the Panasonic 3400mAh cells. I was just being conservative in my estimate of "Actual" mAh rating.

    New Panasonic 3400mAh ( unprotected ) cells can be had for about $11-$12 a cell. Hook them up to a 4-cell PBC and you should get a really good battery for bike use.

    @ sixteenornumber...I can't tell you what mAh rating your battery is. One thing I can say though....You have the same brand name battery as everyone else buying on ebay. That brand is called "Jack Crap".

  12. #12
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    Quote Originally Posted by Cat-man-do View Post
    @ sixteenornumber...I can't tell you what mAh rating your battery is. One thing I can say though....You have the same brand name battery as everyone else buying on ebay. That brand is called "Jack Crap".
    ahh yes, i'm familiar with this brand!

    I didn't expect the batteries to be all that great but one of the packs is actually working quite well. I'm getting just under 3 hours off the T6 bulb. In other news, I bought 4 panasonicsfrom the ebay link I posted before. The seller says they have been tested and conform to specs. I'll post pics and a review of the batteries from that seller once i get them in.

    In the mean time, I had a year old 12cell HP battery that i took apart today, I soldered up an 8cell pack. The pack was still working great before I disassembled it. The cells are Sony US18650GR. everything is soldered up and working great so far.

    :::UPDATE:::

    the 8cell US18650GR is everything i needed! I haven't tested it on medium or low yet but the test on high appears to be 3x the battery life of the crap brand 4cell.

    home brewed battery back  - 18650? 26650?-t6r6-life2_zps0c1fe078.png
    Last edited by sixteenornumber; 02-12-2013 at 04:42 AM. Reason: update

  13. #13
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    I'm using Xtar protected cells -supposedly rebranded Panasonics and i'm getting 3+ hrs of burn time on 1xXML on high.

    You should be able to find the correct jack at your local electronics/hobby store. Mine was a female 2.5mm inline DC Power Jack.
    There are varying sizes on these lights so it's best to take your jacks to the store to confirm your size.

    THey have them on Ebay for cheap
    10 Pcs 2 5x5 5mm DC Power Female Plug Jack Adapter Connector Inline Socket CCTV | eBay


    Quote Originally Posted by sixteenornumber View Post
    2 questions,

    1) I've seen some batteries like the Panasonics go for a little too much money. I would like to get at least 3 hours out of a pack, can you recommend some 18650s?

    2) anyone know where I can buy the female side of the power cable for the pack?

    :::EDIT:::
    you were 100% right on the bad cell thing. i wasn't paying attention to which battery pack (i have 2) I used for the tests. I'm retesting the medium and high on the other battery pack. I'm 30min in right now and so far it's looking like it's going to last 2 times as long. I'll update when i'm done.
    Last edited by spartacus001; 02-12-2013 at 08:08 AM.

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